Multilayer optical films are used in a wide variety of applications. One particular use of multilayer optical films is in mirrors and polarizers that reflect light of a given polarization and wavelength range. Such reflective films are used, for example, in conjunction with backlights in liquid crystal displays to enhance brightness and reduce glare, and in articles, such as sunglasses, to reduce light intensity and glare.
One type of polymer that is useful in making multilayer optical films is a polyester. One example of a polyester-based multilayer optical film includes a stack of polyester layers of differing composition. One configuration of this optical stack includes a first set of birefringent layers and a second set of isotropic layers stacked with the layers in an alternating configuration such that multiple interfaces for reflecting light are formed. The multilayer optical film may also include one or more non-optical layers which, for example, cover at least one surface of the optical stack to prevent damage to the stack during or after processing. Other configurations of layers are also known.